9/20/2007 @ 6:00PM

Methodology

The late John Paul Getty once observed, “If you know exactly how rich you are, you’re not really rich.” We don’t pretend to know exactly, either, but we can get pretty close.

Our estimates of net worth are deliberately conservative and should be considered “at least” figures. We do our best to value everything, including stakes in publicly traded and privately held companies, real estate holdings and investments in art, yachts and mansions. We spend time traveling the country looking for billionaires who would prefer we left them off this special report. We interview employees, competitors, customers, ex-wives and securities analysts. We dig through SEC documents, court records, probate records and newspaper articles. We also take a hard look at debt.

However, we do not pretend to know what is listed on everyone’s private balance sheet. (That is, unless a private balance sheet is provided to us. Three billionaires showed us theirs this year, and we took steps to verify their veracity.)

Our estimates are a snapshot of wealth on Aug. 31, 2007, the day we priced publicly traded shares. Some of those on our list will become richer or poorer within weeks–even days–of publication. All numbers have been rounded to the nearest $100 million, except for fortunes exceeding $20 billion, which are rounded to the nearest $1 billion. Privately held companies are valued by coupling estimates (or in many cases company-provided numbers) of revenues or profits to prevailing price-to-revenues or price-to-earnings ratios for similar public companies. We have not included dispersed fortunes (Du Pont, Kennedy) when individual net worths are below our minimum.

However, we add “& family” to someone’s entry if the immediate relatives of the individual have a direct influence on or stake in a particular fortune but the wealth and its source can ultimately be traced to one individual.